1. Field of the Invention
This invention relates to a new, water-soluble, high concentrated and efficient, powdery or granular herbicidal formulation comprising so-called glyphosate in free acid form.
2. Description of the Prior Art
Glyphosate acid, which is also designated N-phosphonomethylglycine (HOOCCH.sub.2 NHCH.sub.2 PO(OH).sub.2), and especially salts of said acid are known as an effective total post-emergent herbicide such as will appear from the book "The Herbicide Glyphosate" by E. Grossbard and D. Atkinson, Butterworth & Co. Ltd., 1985, ISBN 0-408-11153-4.
Several processes for the preparation of glyphosate are described in the literature, e.g., in U.S. Pat. Nos. 3,977,860 and 4,486,358. Normally the glyphosate is isolated as the free acid, the easiest way to isolate the pure product.
In the following a clear distinction should be made between the glyphosate free acid, the formulation of which is the subject of the present invention, and glyphosate salts, the formulation of which is the subject of most other inventions in this field.
The known marketed formulations contain glyphosate salts and most commonly the isopropylamine salt. A conventional formulation is known under the name of Roundup.
Patent publications dealing with such formulations are U.S. Pat. Nos. 4,405,531 and 3,799,758, EP Published Specification No. 274,369, the Specification of Danish Patent Application No. 2348/88 and GB Published Specification No. 2,098,481.
Said types of formulations are not to be discussed in more detail since they are outside the scope of the present invention.
Further to be mentioned is a "formulation of glyphosate acid" which is mentioned in BCPC Monogram No. 28 from 1985 by D. J. Turner and P. M. Tabbush. A closer study of same shows, however, that it does not concern an acid, formulation, as the acid by heating at 100.degree. C. for one hour, reacts with an excess of a fatty amine in water, and the glyphosate acid is thereby converted to a salt.
EP Patent Specification No. 206,537 also describes a solid, including a powdery or granular formulation of glyphosate derivatives. Said formulation is prepared by melting a surface-active agent, and the glyphosate compound is added in a concentrated solution by means of a solvent. Afterwards the solvent is then removed. However, in said patent specification no examples are mentioned where the glyphosate is used as the free acid, and this is understandable as the solubility of the free acid is so low that the process according to EP Patent Specification No. 206,537 is inapplicable to a free acid formulation.
In Research Disclosure, November 1986, 27161, a wettable powder formulation of glyphosate acid is described; however, as it clearly appears said formulation is not a water-soluble formulation and thus is outside the scope of the present invention as will appear from the following.
The above publications are herein incorporated by reference.
The fact is that it has now surprisingly been found that a simple combination of a certain powdery surface-active agent and the glyphosate acid provides a water-soluble free-flowing formulation having a herbicidal activity that is better than or at least as good as the activity of Roundup and having a substantially better cost-efficiency ratio.